Abstract:

Three-dimensional elasto-plastic finite element method (EP-FEM) based on strength reduction technique is an effective numerical method to evaluate the slope stability. However, this approach is seldom employed to analyze the stability and failure mechanism for a 3-D slope under complex geological environments and local surcharge. The strength reduction numerical method is extended by combination with several typical cases. The effect of many factors, such as element size, boundary condition, soil strength, local surcharge on the slope top and the seismic loads, on the slope stability and the potential sliding surface is discussed in detail. On the basis of this, a typical 3-D slope including soft interlayer and ground water is investigated to elucidate the failure mode and sliding mechanism under the framework of strength reduction FEM, local surcharge on the slope top and seismic loads are also considered in the present analysis. The calculated results indicate the following understandings: 1)With an increase of cohesion, locations of potential slip surface and out-slip point are respectively far away from the toe and the top of slope; 2)An overall slope failure is observed under a low surcharge, while a local foundation failure is found under a high surcharge on the top of slope; 3)When the groundwater is considered, the slope stability reduces, the slip depth and the volume of sliding body increase; 4)The potential sliding surface shows a fold-line in a 3-D slope containing a soft interlayer， the failure mode and sliding mechanism of the slope is completely different under two cases as local surcharge on the slope top and seismic loadings. For the former, a combined failure mode with vertical shear and horizontal dislocation is observed, while for the latter a horizontal dislocation along the soft interlayer is found.

Key words: slopes stability, failure mode, strength reduction finite element method (FEM), surcharge, seismic loads